Treatment of absorbent material



Patented Aug. 1, 1933 UNITED STATES 1,920,438 TREATMENT OF ABSORBENT MATERIAL Charles P. Spaetli, Woodbury, N. J., assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a Corporation of Delaware No Drawing.

Application November 13, 1931 Serial No. 574,916

17 Claims.

My invention relates to a method of impregnating absorptive material for use in explosive compositions and more particularly, to a method of impregnating a plant tissue with organic and 5 inorganic materials of suitable nature.

The usual non-gelatinous dynamite compositions are comprised principally of an explosive material such as nitroglycerin, which may be replaced in part by ammonium nitrate if desired,

carbonaceous combustible materials such as wood pulp, starch, meals, and the like, for absorbing the liquid explosive, and an oxidizing agent such as sodium nitrate, to supply oxygen for complete combustion of the carbonaceous material.

In explosive compositions such as the above,

the non-explosive ingredients are customarily mixed mechanically previous to their incorporation with the liquid explosive. While such a 0 mixture is sufiiciently intimate so that satisfactory strength results from the reaction of the carbonaceous materials with the oxidizing agents, the reaction does not proceed as rapidly as when such-oxidizing and reducing agents are present in a more closely associated condition.

Attempts have been made to bring about a more intimate mixture of the absorptive oxidizing ingredients in explosive compositions by impregnation of the carbonaceous materials with a water solution of ammonium nitrate, sodium nitrate or other salt, rich in oxygen. The water is then removed from the mixture by drying it at an elevated temperature. A great disadvantage in such a process of impregnation is that the material is diflicult to dry and that the high temperaturesnecessary for drying of such relatively easily ignited mixtures, makes the process distinctly hazardous and unsafe in plant practice.

Stoops, in U. S. Patent 1,671,792, alleges to have removed some of the disadvantages of the above process by fusing together an explosive salt, an oxidizing salt and a salt containing water of crystallization. The melt obtained is used for.

impregnation without further addition of water. However, this water of crystallization remains in the finished explosive composition as undesirable material and results in decreased strength of the explosive compound.

One of the objects of my invention is to impregnate carbonaceous absorbent materials with one or more inorganic salts in a new and improved manner. Another object is the production of this impregnating composition by a methed that is less dimcult to perform and which involves less hazard. A further object is the production of impregnated absorptive materials comprising inorganic salts, by a method which requires no subsequent drying, the product being substantially free of water as made. Still further objects will be apparent as the invention is described more fully hereinafter.

It has long ago been pointed out that urea formed compounds with inorganic salts and in particular, inorganic nitrates. These compounds were formed in either aqueous or in alco- 85 holic solution depending upon the particular inorganic nitrate employed. The new compounds, which were separated by careful evaporation of the solvents, were shown to have definite crystal structure and in most cases no longer gave the characteristic qualitative reactions of their con-' stituents.

I have now discovered that many of these compounds may be more easily formed by fusing together the proper proportions of urea, and the inorganic salt at temperatures of '70 to 120 C. These new compounds may if desired be grained out or granulated when slowly cooled and agitated.

I have further discovered that many of these compounds of urea with organic salts are excellent solvents for ammonium nitrate and also for ammonium nitrate and sodium nitrate or other inorganic nitrates. For example, eight parts of the ureaammonium nitrate compound will readily form a clear solution with 50-60 parts of ammonium nitrate and in addition, will also dissolve. 8 to 10 parts of sodium nitrate at a temperature of about 100 to 120 C. Compounds of urea with calcium nitrate, magnesium nitrate or sodium nitrate are equally good solvents for ammonium nitrate.

I have furthermore found that these urea-inorganic salt solutions of inorganic nitrates are especially well adapted for the impregnation of,

carbonaceous combustible absorbent materials for use in dynamite compositions. I generally prefer to use ammonium nitrate with urea for this purpose although other inorganic nitrates may be used, as for example, sodium nitrate, calcium nitrate, magnesium nitrate; potassium nitrate, and like compounds.

It has been found urmecessary to first form and separate the composition of urea and the inorganic salt. It is only necessary to mix the urea with a suitable portion of ammonium nitrate and heat until a clear melt is formed which step requires a temperature of about 70 C. To this may then be added slowly the balance of the ammonium nitrate to be used, increasing the temperature as necessary to obtain a clear melt.

According to one embodiment of my invention, I effect the impregnation of the carbonaceous combustible material such as wood pulp, for example, by adding it in suitable quantity to the solution formed by dissolving an inorganic nitrate or nitrates in the composition of.urea and ammonium nitrate or other inorganic nitrate. This solution is caused to permeate and to be thoroughly distributed within the pores and voids, and to substantially coat the surface of the absorbent material. The impregnated product is slightly cooled and removed at once to moisture-tight .containers. When completely cooled it is ready for use in explosive compositions. It requires no subsequent drying and contains substantially no water that would depreciate explosive strength.

While compositions of urea with one nitrate have been mentioned above, it is frequently advantageous to employ more than one inorganic nitrate in the melt to be used for impregnation. Because of the oxygen deficiency for complete combustion of urea it would be undesirable to use a high proportion of this ingredient. I find that satisfactory'low temperature solutions may be prepared containing relatively small percentages of urea. Very satisfactory compositions are obtained using urea with the ammonium nitrate and sodium nitrate, with ammonia nitrate and calcium nitrate and with various other combinations of nitrates. While I have cited urea 'as a medium for producing low temperature melts of inorganic nitrates, it isfrequently advantageous to employ other organic compounds. For example I mayus'e for this purpose, dicyandiamide, quanidine nitrate, acetamid, and like compounds.

My invention is important particularly in the field of the so-called anmionia permissibles which are the explosives used most commonly in coal mining. With such explosives, high percentages of ammonium nitrate are customarily used with a relatively small amount of nitroglycerin as a s'ensitizer. In such compositions, it is desirable that the sensitiveness of the explosive be maintained at as high a degree as is possible while keeping the nitroglycerin content at a minimum. These desirable properties are obtained by the product resulting from my invention.

.By way of further illustration of my invention I may cite the following compositions, although it is to be understood that these embodiments are only illustrative and that I amnot in any way to be limited thereby:

I II

Nitroglycerin. l5. 0 Ammonium nitr 56. 0 Sodium nitrate." Q 5. 0 Calcium nitrate 4. 0 I. pith.. .0 17.0 Urea 0 4. 0

number of cartridges of explosive per unit weight or per case. a

The impregnated material made according to my invention, has a lowered absorptive power for nitroglycerin as compared to a mechanical mixture of the same ingredients, which fact allows the use of a minimum proportion of sensitizer for the maintenance of good sensitivity. This sensitivity is easily maintained even under the adverse condition of long storage. Furthermore, my impregnation process so reduces the absorption ability of the combustible for liquid explosives that as a result the liquid explosive is confined to the surface of the particles with resulting increased sensitiveness. The use of my impregnated material also favors the production of explosive compositions containing ammonium nitrate which resist setting or hardening in warm storage.

While I have described my invention at length in the foregoing, it is to be understood that the details may vary within a wide scope without departing from the spirit of the invention. For example, while I have cited bagasse pith as the carbonaceous ingredient for impregnation, any desired carbonaceous material may be used in its place, such, for example, as corn stalk pith, Sphagnum moss, and the like. As sensitizing material, either nitroglycerin or nitroglycerin solutions of any of the common freezing point depressants may be used, such, for example, as ethylene glycol dinitrate, nitrated sugar, nitrated polymerized glycerin, and the like.

I therefore intend to be limited only as indicated in the following patent claims:

I claim:

1. The process of producing a dynamite ingredient which comprises fusing ammonium nitrate with urea, permitting the melt $0 permeate and be thoroughly absorbed by an absorptive material, and cooling the impregnated absorptive material so that the melt will solidify within the pores and voids and substantially coat the surface of the absorptive material.

2. The process of producing a dynamite ingredient which comprises preparing a composition of urea with an inorganic nitrate by fusing suitable amounts of these materials together, dissolving in the melt further amounts of an inorganic nitrate or nitrates, increasing the temperature of the solution by the further application of heat until a substantially clear solution is obtained, and subjecting an absorptive material to the solution so that the solution is thoroughly absorbed by the absorptive material, and cooling the impregnated absorptive material.

3. The process of producing an explosive which comprises preparing a composition of urea with ammonium nitrate by fusing suitable amounts of these materials together by the application of heat, dissolving in the melt further amounts of ammonium nitrate and sodium nitrate, increasing the temperature of the solution by further application of heat until a substantially clear solution is obtained, and subjecting an absorptive mate rial to the solution so that the solution is thoroughly absorbed by the absorptive material, and cooling the impregnated absorptive material. 4. The process of preparing a carbonaceous absorbent material which comprises impregnating an absorbent material with a molten compound of urea with an inorganic nitrate.

5. The process of preparing a carbonaceous absorbent material for use in explosive compositions which comprises impregnating the absorbent material with a molten compound of urea with an inorganic nitrate, said molten compound containing one or more additional inorganic nitrates dissolved therein.

6. The process of preparing a carbonaceoeus absorbent material for use in explosive compositions which comprises impregnating a plant tissue with a molten compound of urea with an inorganic nitrate, said molten compound containing one or more inorganic nitrates dissolved therein.

'7. The process of preparing a carbonaceous absorbent material for use in explosive compositions which comprises impregnating bagasse pith with a molten compound of urea with ammonium nitrate, said molten compound containing additional ammonium nitrate dissolved therein.

8. The process of preparing a carbonaceous absorbent material for use in explosive compositions which comprises impregnating corn stalk pith with a molten compound of urea with sodium nitrate, said molten compound containing ammonium nitrate dissolved therein.

9. The process of preparing a carbonaceous absorbent material for use in explosive composi-. tions which comprises impregnating vegetable fiber with a molten compound of urea with calcium nitrate, said molten compound containing ammonium nitrate and sodium nitrate dissolved therein.

10. A process of producing a dynamite ingredient which comprises fusing one or more inorganic nitrates with urea, impregnating an absorbent material with the melt, and cooling the impregnated absorbent material.

11. An explosive composition comprising a sensitizing ingredient and a carbonaceous absorbent material impregnated with a compound of urea and an inorganic nitrate.

12. An explosive composition comprising a sensitizing ingredient and a plant tissue impregnated with a compound of urea with an inorganic salt and an inorganic nitrate.

13. An explosive composition comprising a sensitizing ingredient and a vegetable fiber impregnated with a compound of urea with an inorganic salt and ammonium nitrate.

14. An explosive composition comprising a liquid explosive ingredient as sensitizing agent and an absorbent material impregnated with ammonium nitrate, sodium nitrate, and a compound of urea with calcium nitrate.

15. An explosive composition comprising nitroglycerin and an absorbent material impregnated with an explosive salt, an oxidizing salt, and a compound of urea with an inorganic nitrate.

16. An explosive composition comprising nitroglycerin and bagasse pith impregnated with ammonium nitrate, sodium nitrate, and a compound of urea with ammonium nitrate.

17. An explosive composition comprising nitroglycerin and cornstalk pith impregnated with ammonium nitrate, sodium nitrate, and a compound of urea with sodium nitrate.

CHARLES P. SPAETH.

CERTIFICATE OF CORRECTION.

Patent No. 1,920,438.

August 1, 1933.

CHARLES P. SPAETH.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Page 1, line 81, for

"organic" read "inorganic"; page 2, lines 5660, in the table before each of the words, "Ammonium nitrate, Sodium nitrate, Calcium nitrate, Bagasse pith, and Urea" insert the parentheses and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signedand sealed this 19th day of September.

(Seal) M. J. Moore. Acting Commissioner of Patents. 

